When the US inventory of the 128GB version of Microsoft's Surface Pro tablet dried up within hours after going on sale Saturday, there were plenty of disappointed shoppers. But there were also many skeptics who charged that Microsoft artificially created the sell-out by under-stocking the US$1000 units at its online store, Best Buy and Staples.

By the way, there's no shortage of the $900, 64GB versions of the tablet.

Microsoft's official statement is that the shortage was caused by an underestimate in demand, although there were plenty of voices on Reddit who found stores with either no 128GB units or a paltry number of them for sale.

And perhaps Chris Cook of the small consumer electronics blog Product Reviews put it most succinctly: "While Microsoft would have you believe that they are working on the lack of supply problems, we're more inclined to say that this was all part of their plan," Cook wrote.

Why hold back?

Others are discounting the artificial sell-out theory. "People build a product based on what they think can sell," Stephen Baker, a consumer electronics analyst with the NPD Group in New York City said in an interview.

"I really don't think any retailer would purposely not buy Surface Pros so Microsoft could say it was going to sell out," he added. "There's no way that would ever happen."

If retailers didn't get a lot of 128GB Surface Pros, it was because Microsoft didn't have a lot of product or because of the lackluster sales numbers for Surface RT--Microsoft's first branded tablet--retailers ordered few of the Pro, Baker said.

Supply manipulation accusations are common when a product sells out, Baker said. "There's always those kinds of rumors," Baker said. "It flies in the face of logic, if a company wants to make money."

"The goal is to sell stuff," he added, "not to pretend you sold what you didn't have."

Companies and retailers maintain inventories based on what they think will sell, Baker added. "Everybody expected that [the Surface Pro] would not be a huge seller," he said. "It's expensive and the previous product didn't do very well so anyone wouldn't have built a lot of them."

"Did they sell out because retailers only had two or three per store?" he asked. "Maybe, but I don't see anything in the previous volumes of the previous product that would indicate this was going to be a huge seller."

Pro is the stronger Surface

Still, other than the controversial sell-out claim, signs indicate that the Surface Pro may have stronger legs than the Surface RT has in the market. For example, a study released by Forrester Research found that a Microsoft tablet was a most desired item for many tech workers.

Of course, Microsoft could settle the sell-out controversy by releasing sales numbers for Surface Pro. If the company sold a million units, then all the conspiracy theorists would go away. If it sold 6000 units, then maybe the skeptics might have a point about supply manipulation.

That's not likely to happen, though, since Microsoft hasn't even released the official numbers for Surface RT sales.

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